From the Guidelines
It is necessary to obtain an estimated Glomerular Filtration Rate (eGFR) blood test before a Computed Tomography (CT) scan to assess renal function and determine the safety of administering contrast media, as patients with decreased renal function are at risk of contrast-induced nephropathy (CIN) 1. The eGFR is a crucial indicator of renal function, and knowing a patient's renal function before a CT scan with contrast is essential, as some contrast agents can be nephrotoxic, particularly in patients with impaired renal function. Key considerations for patients with decreased renal function include:
- Avoiding contrast administration if eGFR is below a certain threshold (typically 30-45 mL/min/1.73 m²) 1
- Reducing the contrast dose in patients with borderline renal function
- Choosing an alternative, less nephrotoxic contrast agent
- Implementing preventive measures, such as fluid treatment before and after scanning The eGFR blood test should be taken within 3 months before the scan, or more recently if the patient has known kidney disease or risk factors for acute kidney injury. By taking this precaution, the risk of contrast-induced nephropathy, a potentially severe complication that can lead to acute kidney failure, is minimized 1.
From the Research
Importance of eGFR Testing Before CT Scans
- The estimated Glomerular Filtration Rate (eGFR) blood test is necessary before a Computed Tomography (CT) scan to assess the risk of renal dysfunction, particularly in patients who will be administered iodinated contrast medium 2, 3, 4, 5, 6.
- eGFR testing helps identify patients with reduced kidney function, which can increase the risk of contrast-induced acute kidney injury (CI-AKI) 4, 5.
- The American College of Radiology/National Kidney Foundation (ACR/NKF) consensus statement provides guidelines for screening patients for risk of renal dysfunction before administration of iodinated contrast medium 2.
Risk Factors for Renal Dysfunction
- Patient-reported risk factors, such as dialysis, kidney disease, prior kidney surgery, diabetes mellitus, hypertension, and multiple myeloma, can help identify patients who require eGFR testing before CT scans 2.
- However, commonly applied risk factors may not be independently associated with low eGFR, and the use of ACR/NKF criteria can substantially reduce eGFR testing while minimizing the risk of missing patients with renal dysfunction 2.
- Additional patient-related risk factors, such as age and presence of chronic kidney disease (CKD), can also impact the risk of CI-AKI 4, 5.
Safety and Utility of eGFR Testing
- Deferring eGFR testing in low-risk emergency department patients can improve operational performance and reduce the number of patients requiring testing, while maintaining safety 3.
- The use of reduced doses of iso-osmolar contrast agents can minimize the risk of CI-AKI in high-risk oncology patients with impaired renal function 4.
- Long-term studies have shown that intravenous contrast media used in standard CT scans have no significant long-term effects on renal function in CKD patients 5.
- Using eGFR values rather than serum creatinine levels can facilitate the identification of patients with renal insufficiency and provide a more accurate assessment of kidney function 6.